MIS-C: Rare but severe
The authors of the statement explain that children and some young adults may develop MIS-C, a relatively rare but severe inflammatory syndrome generally occurring 2-6 weeks after infection with SARS-CoV-2 that can affect the heart and multiple organ systems.
In the first year of the pandemic, more than 2,600 cases of MIS-C were reported to the Centers for Disease Control and Prevention, at an estimated rate of 1 case per 3,164 cases of SARS-CoV-2 infection in children, with MIS-C disproportionately affecting Hispanic and Black children.
As many as 50% of children with MIS-C have myocardial involvement, including decreased left ventricular function, coronary artery dilation or aneurysms, myocarditis, elevated troponin and BNP or NT-proBNP, or pericardial effusion. Acute-phase reactants, including C-reactive protein, D-dimer, ferritin, and fibrinogen, can be significantly elevated in MIS-C, neutrophil/lymphocyte ratio may be higher, and platelet counts lower than those with non–MIS-C febrile illnesses.
Fortunately, the outcome of MIS-C is generally very good, with resolution of inflammation and cardiovascular abnormalities within 1-4 weeks of diagnosis, the report says.
However, there have been reports of progression of coronary artery aneurysms after discharge, highlighting the potential for long-term complications. Death resulting from MIS-C is rare, with a mortality rate of 1.4%-1.9%.
Compared with children and young adults who died of acute SARS-CoV-2 infection, most of the fatalities from MIS-C were in previously healthy individuals without comorbidities.
The authors recommend structured follow-up of patients with MIS-C because of concern about progression of cardiac complications and an unclear long-term prognosis.
The statement notes that the first-line treatment for MIS-C is typically intravenous immunoglobulin (IVIG) and patients with poor ventricular function may need to have IVIG in divided doses to tolerate the fluid load.
Supportive treatment for heart failure and vasoplegic shock often requires aggressive management in an ICU for administration of inotropes and vasoactive medications. Antiplatelet therapy with low-dose aspirin is considered in patients with coronary artery involvement, and anticoagulation is added, depending on the degree of coronary artery dilation.
The statement notes that vaccines can prevent patients from getting COVID-19 and decrease the risk of MIS-C by 91% among children 12-18 years of age.
On vaccine-associated myocarditis, it concludes the benefits of getting the vaccines outweigh the risks.
For example, for every 1 million doses of the mRNA COVID-19 vaccines in males ages 12-29 years (the highest risk group for vaccine-associated myocarditis), it is estimated that 11,000 COVID-19 cases, 560 hospitalizations, and six deaths would be prevented, whereas 39-47 cases of myocarditis would be expected.
But it adds that the CDC is continuing to follow myocarditis in children and young adults closely, particularly a possible connection to the mRNA COVID-19 vaccines.
The statement says that more research is needed to better understand the mechanisms and optimal treatment approaches for SARS-CoV-2 infection, vaccine-associated myocarditis, the long-term outcomes of both COVID-19 and MIS-C, and the impact of these various conditions on the heart in children and young adults. In addition, any new antiviral therapies need to be tested in clinical trials focused on children.
“Although much has been learned about how the virus impacts children’s and young adult’s hearts, how to best treat cardiovascular complications, and prevent severe illness, continued clinical research trials are needed to better understand the long-term cardiovascular impacts,” Dr. Jone said. “It is also important to address health disparities that have become more apparent during the pandemic. We must work to ensure all children receive equal access to vaccination and high-quality care.”
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